Sphingosine kinase 1 is a potential therapeutic target for nasopharyngeal carcinoma

Machine learning models to identify lead compound and substitution optimization to have derived energetics and conformational stability through docking and MD simulations for sphingosine kinase 1

Sphingosine kinases (SphKs) are a group of important enzymes that circulate at low micromolar concentrations in mammals and have received considerable attention due to the roles they play in a broad array of biological processes including apoptosis, mutagenesis, lymphocyte migration, radio- and chemo-sensitization, and angiogenesis. In the present study, we constructed three classification models by four machine learning (ML) algorithms including naive bayes (NB), support vector machine (SVM), logistic regression, and random forest from 395 compounds. The generated ML models were validated by fivefold cross validation. Five different scaffold hit fragments resulted from SVM model-based virtual screening and docking results indicate that all the five fragments exhibit common hydrogen bond interaction a catalytic residue of SphK1. Further, molecular dynamics (MD) simulations and binding free energy calculation had been carried out with the identified five fragment leads and three cocrystal inhibitors. The best 15 fragments were selected. Molecular dynamics (MD) simulations showed that among these compounds, 7 compounds have favorable binding energy compared with cocrystal inhibitors. Hence, the study showed that the present lead fragments could act as potential inhibitors against therapeutic target of cancers and neurodegenerative disorders.

Clinical relevance of CERK and SPHK1 in breast cancer and their association with metastasis and drug resistance

Despite numerous reports on the altered sphingolipids metabolism in human cancers, their clinical significance in breast cancer remains obscure. Previously, we identified the high levels of sphingolipids, ceramide phosphates and sphingosine phosphates, and the genes involved in their synthesis, CERK and SPHK1, in breast cancer patients. The present study aimed to determine the correlations of CERK and SPHK1 with clinical outcomes as well as metastasis and drug resistance markers. Both local and TCGA cohorts were analysed. High-confidence regulatory interaction network was constructed to find association of target genes with metastasis and drug resistance. Furthermore, correlations of CERK and SPHK1 with selected metastasis and drug resistance markers were validated in both cohorts. Overexpression of CERK and SPHK1 was associated with nodal metastasis, late tumor stage and high proliferation potency. In addition, increased CERK expression was also indicative of poor patient survival. Computational network analysis revealed the association of CERK and SPHK1 with known metastasis markers MMP-2 and MMP-9 and drug resistance markers ABCC1 and ABCG2. Correlation analysis confirmed the associations of target genes with these markers in both local as well as TCGA cohort. The above findings suggest clinical utility of CERK and SPHK1 as potential biomarkers in breast cancer patients and thus could provide novel leads in the development of therapeutics.

Sphingosine kinase 1 contributes to doxorubicin resistance and glycolysis in osteosarcoma

Osteosarcoma (OS) is one of the most common and aggressive malignancies in children and adolescents worldwide. Sphingosine kinase 1 (SphK1) has recently been reported to serve a role in OS progression. The present study aimed to investigate the role of SphK1 in the development of chemoresistance and glycolysis in OS cell lines. SphK1 expression levels in OS cell lines (U2OS, MG63 and SaoS2) were analyzed using western blotting and reverse transcription-quantitative PCR (RT-qPCR). A cell survival assay was conducted to determine doxorubicin-resistance in OS cells, and glycolysis was also evaluated. SphK1 expression was increased in the U2OS and SaoS2 cell lines, and both cell lines were more resistant to doxorubicin when compared with the MG63 cell line. SphK1 knockdown or overexpression altered doxorubicin resistance and the viability of OS cell lines. In addition, hypoxia inducible factor-1α (HIF-1α) expression was positively associated with SphK1 expression, and partly mediated SphK1-induced effects on doxorubicin resistance and glycolysis. The present study suggested that SphK1 participated in the development of doxorubicin resistance and contributed to glycolysis in OS cells by regulating HIF-1α expression. However, further studies investigating the application of SphK1 associated therapies for patients with OS are required.

MORF4L1 suppresses cell proliferation, migration and invasion by increasing p21 and E-cadherin expression in nasopharyngeal carcinoma

Mortality factor 4-like 1 (MORF4L1) is a member of a subgroup of histone acetyltransferases and belongs to the mortality factor on chromosome 4 (MORF4) class of proteins. However, the role of MORF4L1 in cancers is largely unknown. Using reverse transcription-quantitative polymerase chain reaction and published datasets, the present study demonstrated that the expression of MORF4L1 is decreased in several cancers, including nasopharyngeal carcinoma (NPC). Additionally, the methylation rate of the promoter of MORF4L1 was identified to be significantly higher in tumour cells than in normal cells. The ectopic expression of MORF4L1 was also revealed to inhibit cell proliferation, colony formation, migration and invasion in NPC, whereas the knockdown of MORF4L1 promoted cell proliferation, colony formation, migration and invasion. Mechanistically, the present study demonstrated that MORF4L1 functions as a tumour suppressor by increasing p21 and E-cadherin levels. These findings may be useful novel targets for treating patients with NPC.

SPHK1 promotes metastasis of thyroid carcinoma through activation of the S1P/S1PR3/Notch signaling pathway

Thyroid carcinoma is characterized by an aggressive behavior, lack of effective targeted therapies and a high rate of relapse. Sphingosine kinase 1 (SPHK1) has been reported to be a critical regulatory factor in the progression of thyroid carcinoma, but the correlation between SPHK1 and clinical prognosis of patients with thyroid carcinoma has remained to be fully elucidated. The present study aimed to systematically assess the roles of SPHK1 in thyroid carcinoma metastasis and further investigate the possible underlying mechanisms. First, the expression of SPHK1 was detected in tissue samples from 53 thyroid carcinoma patients and in thyroid carcinoma cell lines by reverse transcription-quantitative polymerase chain reaction analysis. Furthermore, the level of phospho-(p)-SPHK1 was immunohistochemically detected in human thyroid carcinoma tissue samples. The activity of SPHK1 was measured with a commercial SPHK1 Activity Assay kit. A sphingosine-1-phosphate (S1P) competitive ELISA kit was used to determine the extracellular S1P levels. The metastatic potential was assessed by a Transwell assay. In addition, the association between SPHK1 and clinicopathological features of the patients was analyzed. The results indicated that the expression of SPHK1 in thyroid carcinoma samples was significantly higher than in paired adjacent normal thyroid tissues. High levels of SPHK1 were positively correlated with poor overall survival and progression-free survival. Downregulation of SPHK1 by lentiviral vector expressing SPHK1 small interfering (si)RNA evidently repressed Notch signaling and reduced the migration and invasion of thyroid carcinoma cells in vitro and in a NOD/SCID mouse model. Furthermore, inhibition of SPHK1 by siRNA or treatment with SPHK1 inhibitor 5C sensitized thyroid carcinoma to cisplatin and doxorubicin. In addition, it was demonstrated that silencing of SPHK1 effectively inhibits processes associated with thyroid carcinoma metastasis through the Notch signaling pathway, and SPHK1 may therefore represent a potential therapeutic target in thyroid carcinoma. In conclusion, the present study indicated that high levels of p-SPHK1 were positively correlated with high levels of S1P which in turn promoted thyroid carcinoma metastasis via the S1P/S1P receptor 3/Notch signaling pathway, suggesting possible prognostic markers and therapeutic targets.

Lin28B facilitates the progression and metastasis of pancreatic ductal adenocarcinoma

Lin28B, a Lin28 homologue, represses the biogenesis of let-7 microRNAs (miRNAs), has a role in tumorigenesis, and is considered a potential therapeutic target for various human malignancies. However, the associations between Lin28B and the clinical features and outcomes of patients with pancreatic ductal adenocarcinoma (PDAC) remain unclear. In this study, we explored the clinical significance of Lin28B in PDAC and its association with metastasis by examining tissues from patients with PDAC and elucidated the molecular mechanisms using PDAC cell lines. In patients, high Lin28B expression was significantly correlated with high levels of lymphatic metastasis, distant metastasis and a poor prognosis. Furthermore, the multivariate analysis identified Lin28B expression as an independent prognostic factor in patients. In cell lines, stable silencing of Lin28B inhibited cell proliferation, cell cycle transition, migration and the epithelial-mesenchymal transition (EMT). It also increased the expression of the c-MYC, HMGA2 and KRAS genes, which are targeted by the cancer-suppressor miRNA let-7. Lin28B overexpression in the PDAC cell lines had the opposite effect. In human PDAC samples, high Lin28B expression was associated with decreased let-7 expression and increased c-MYC, HMGA2 and KRAS expression. Thus, Lin28B is a novel marker for predicting the prognosis of patients with PDAC and might be a potential therapeutic target for PDAC.

FTY720 inhibits mesothelioma growth in vitro and in a syngeneic mouse model

BACKGROUND

Malignant mesothelioma (MM) is a very aggressive type of cancer, with a dismal prognosis and inherent resistance to chemotherapeutics. Development and evaluation of new therapeutic approaches is highly needed. Immunosuppressant FTY720, approved for multiple sclerosis treatment, has recently raised attention for its anti-tumor activity in a variety of cancers. However, its therapeutic potential in MM has not been evaluated yet.

METHODS

Cell viability and anchorage-independent growth were evaluated in a panel of MM cell lines and human mesothelial cells (HM) upon FTY720 treatment to assess in vitro anti-tumor efficacy. The mechanism of action of FTY720 in MM was assessed by measuring the activity of phosphatase protein 2A (PP2A)-a major target of FTY720. The binding of the endogenous inhibitor SET to PP2A in presence of FTY720 was evaluated by immunoblotting and immunoprecipitation. Signaling and activation of programmed cell death were evaluated by immunoblotting and flow cytometry. A syngeneic mouse model was used to evaluate anti-tumor efficacy and toxicity profile of FTY720 in vivo.

RESULTS

We show that FTY720 significantly suppressed MM cell viability and anchorage-independent growth without affecting normal HM cells. FTY720 inhibited the phosphatase activity of PP2A by displacement of SET protein, which appeared overexpressed in MM, as compared to HM cells. FTY720 promoted AKT dephosphorylation and Bcl-2 degradation, leading to induction of programmed cell death, as demonstrated by caspase-3 and PARP activation, as well as by cytochrome c and AIF intracellular translocation. Moreover, FTY720 administration in vivo effectively reduced tumor burden in mice without apparent toxicity.

CONCLUSIONS

Our preclinical data indicate that FTY720 is a potentially promising therapeutic agent for MM treatment.